Place onion, carrot and celery in a food processor and process until very fine pieces. Alternatively you can dice them very fine.
Heat 1 tablespoon olive oil in a medium pot. Add onion mixture and salt cook for 5 minutes, until sweated down.
Add turkey, salt, and pepper and cook, breaking up the turkey, until no pink remains, about 5 minutes.
Add wine and cook until reduced, about 5 minutes.
Add tomato paste, bay leaf and chicken stock and bring up to a gentle simmer.
Simmer for 30-35 minutes, until the liquid has reduced and the sauce is slightly thickened.
Meanwhile, cook pasta according to package instructions.
Once bolognese is finished, turn off heat and mix in (optional) butter. Taste, and adjust seasoning.
Toss pasta with 1 cup of bolognese and divide into 4 bowls. Divide remaining bolognese on pasta and sprinkle with (optional) parmesan cheese. Serve immediately.